The invention relates to apparatus for depositing a dielectric film.
Such devices have been known for some time for the deposition of dielectric films according to the so-called plasma enhanced chemical vapor deposition (PECVD) process.
In the chemical vapor deposition (CVD) process, the reaction partners are combined into the substance forming the film either by already being present in the gas chamber above the surface to be coated, in which case the substance is then deposited on the surface as a condensate (homogeneous reaction), or they are combined only directly on the surface to be coated, with the latter possibly catalytically supporting the process (heterogeneous reaction).
When the PECVD process was employed, it was noted repeatedly that in cases in which the surfaces to be coated were subjected directly to the plasma, the resulting films were damaged to a greater or lesser degree. (See, for example, Schachter et al, J. Vac. Sci. Technol. B4 (1986), pages 1128-1129).
An improvement in the quality of the films was realized with special plasma reactors which have a plasma chamber that is separated from the reaction chamber containing the samples to be coated, known as remote reactors. Thus, in "Solid State Technology," April (1987), page 107, a reactor is described which employs a very complicated excitation by means of electron cyclotron resonance in the magnetic field. In "J. Vac. Sci. Technology," B5 (2), March/April, 1987, a reactor is disclosed in which a plasma is generated by HF excitation and the surfaces to be coated are disposed in a reaction chamber adjacent to the plasma chamber. Electrical shielding against the plasma for the surfaces to be coated does not occur there. The "shutter" shown in FIG. 2 serves only to protect against the deposition of impurities.
The above described reactors are very expensive and demand the precise adherence to many parameters, such as gas composition and throughput, sample temperature and plasma characteristics.